chore(issue-forms): retire local templates -> inherit org canon

Removes this repo's local .github/ISSUE_TEMPLATE override so it inherits the
consistent org-wide issue forms from hyperpolymath/.github (the local set was an
inferior subset of the canon). One design everywhere.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: hyperpolymath